Cellulose hybrid nanocomposites using Napier grass fibers with in situ generated silver nanoparticles as fillers for antibacterial applications.

Initially silver nanoparticles (AgNPs) were in situ generated in Napier grass fibers (NGFs) and these nanocomposite NGFs were used as fillers (by 1 wt% to 5 wt%) in cellulose matrix to make hybrid nanocomposite films. The formation of in situ generated AgNPs on the surface of the NGFs was studied using scanning electron microscope (SEM), high resolution transmission electron microscope (HR-TEM), Energy dispersive X-ray spectroscope (EDX) and X-ray photoelectron spectroscope (XPS). The HR-TEM analysis indicated the presence of spherical AgNPs on the surface of the fillers with a size ranging from 10 to 100 nm but majority of them in the 11 to 20 nm range. The POM images indicated the randomly oriented fillers in the hybrid composite films. Though the inflection temperatures of the hybrid composites were lower than for the matrix (due to catalytic activity of the AgNPs), the residual weight for them was higher than that of the matrix. The tensile strength of the hybrid nanocomposites varied between 73 MPa and 40 MPa while their tensile modulus between 4350 MPa and 2580 MPa for various filler contents. The hybrid nanocomposite films showed good antibacterial activity against Gram negative (E. coli) and Gram positive (S. aureus) bacteria.

All-cellulose composite films with cellulose matrix and Napier grass cellulose fibril fillers.

Diverse move has been attempted to use biomass as a filler for the production of biodegradable all-cellulose composites. In this study, cellulose fibrils (CFs) extracted from native African Napier grass (NG) fibres were used as fillers in cellulose matrix and made all-cellulose composites. Napier Grass Cellulose fibrils (NGCFs) loading was varied from 5 to 25 wt% in cellulose matrix in random orientation and the all cellulose composites were made by regeneration process. These composites were characterized by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction, thermogravimetric analysis, optical microscopy, and tensile testing. The FTIR spectra indicated not only the presence of minute amounts of hemicelluloses and lignin in the filler but also the possible interaction between the matrix and NGCFs. The crystallinity of the all-cellulose composites was found to be lower than that of the cellulose matrix. The thermal stability of the all-cellulose composites was found to be higher than that of the cellulose matrix and increased with NGCFs filler content. The tensile strength of the all-cellulose composites though was lower than that of the cellulose matrix but still was higher than for commodity polymers. The all-cellulose composites can be considered for wrapping and mulching applications.

Synthesis and characterization of cellulose/silver nanocomposites from bioflocculant reducing agent.

Microbial secreted polymers have high molecular weight due to the presence of repeated units of macromolecules. Some of the polymers are derived from natural resources, including marine and soil microorganisms. In nano-biotechnology people are using different biological agents in the preparation of metal nanoparticles. In this study, the microbial bioflocculant polymer was used as an agent in preparation of silver nanoparticles. The prepared nanoparticles were immobilized into the cellulose matrix. The presence of silver nanoparticles inside the cellulose matrix was confirmed by Scanning Electron Microscopic (SEM) and Transmission Electron Microscopic (TEM) analyses. The FTIR characterization studies revealed the presence of silver in the cellulose nanocomposites. The XRD analysis indicated the silver peak formation inside the silver nanocomposites. The thermal degradation studies of silver nanocomposites showed that at 450°C the residual weight was completely decreased. The antibacterial activity of silver nanocomposites was tested against E.Coli bacteria.

Identification and production of bioflocculants by Enterobacter sp. and Bacillus sp. and their characterization studies.

In this work, two bioflocculants, namely, EB-EPS and B1-EPS, were derived from Enterobacter sp. and Bacillus sp., respectively, and analyzed with regard to their production and characterization. About 0.9 and 0.16 g of purified EB and B1 were obtained from I L of fermentation broth. Chemical analysis showed the contents of purified EB and B1 mainly as 88.7 and 92.8% (w/w) of carbohydrate, and 11.3 and 21.8% (w/w) protein, respectively. Fourier-transform infrared spectrometry analysis revealed the presence of hydroxyl, amide, and carboxyl groups in the identified bioflocculant. Thermogravimetric analysis (TGA) results exhibited enhanced thermal stability with a minimum mass loss of 50% while 25% were found to have occurred at higher temperatures (>400°C) for microbe-derived compounds EB and B1 leading to the possibility of using these compounds as fillers or for fabricating composite films for high-temperature applications. Further, the compounds from both the bacteria exhibited good antibacterial characteristics against pathogenic Escherichia coli. Degradability study of bioflocculant-embedded composite films shows the possibility of attaining eco-friendly bioremediation. Accordingly, experimental results revealed the suitability of developed composite films as a suitable alternative for food packaging and biomedical applications.

Cellulose nanocomposite films with in situ generated silver nanoparticles using Cassia alata leaf extract as a reducing agent.

Cotton linters were dissolved in aq. (8% LiOH+15% urea) that was pre-cooled to -12.5°C. Using this solution cellulose gel films were prepared by regeneration method with ethyl alcohol as a coagulant. These wet films were diffused with 10wt% Cassia alata leaf extract that acted as a reducing agent. The leaf extract diffused cellulose wet films were used as the matrix. The wet matrix films were dipped individually in lower concentrated 1-5mM aq.AgNO3 source solutions in the presence of sunlight and allowed the solutions to react with the diffused leaf extract reducing agent which in situ generated the silver nanoparticles (AgNPs) inside the films as well as in the source solution. The AgNPs formed in the source solution were observed by transmission electron microscope (TEM) and scanning electron microscope (SEM) while those formed in situ the films were observed by SEM and the particle size distribution was determined. The cellulose/AgNP composite films showed good antibacterial activity against Escherichia coli bacteria. These nanocomposite films were also characterized by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), thermogravimetric analysis (TGA) and tensile tests. At temperatures below 300°C, the thermal stability of the nanocomposite films was lower than that of the matrix due to the catalytic effect of AgNPs. The nanocomposite films also possessed good tensile properties. The ecofriendly cellulose/AgNP composite films with good antibacterial activity and tensile properties can be considered for medical applications like dressing materials.

Preparation and properties of cellulose nanocomposite films with in situ generated copper nanoparticles using Terminalia catappa leaf extract.

In the present work, copper nanoparticles (CuNPs) were in situ generated inside cellulose matrix using Terminalia catappa leaf extract as a reducing agent. During this process, some CuNPs were also formed outside the matrix. The CuNPs formed outside the matrix were observed with transmission electron microscope (TEM) and scanning electron microscope (SEM). Majority of the CuNPs formed outside the matrix were in the size range of 21-30nm. The cellulose/CuNP composite films were characterized by Fourier transform infrared spectroscopic, X-Ray diffraction and thermogravimetric techniques. The crystallinity of the cellulose/CuNP composite films was found to be lower than that of the matrix indicating rearrangement of cellulose molecules by in situ generated CuNPs. Further, the expanded diffractogram of the composite films indicated the presence of a mixture of Cu, CuO and Cu2O nanoparticles. The thermal stability of the composites was found to be lower than that of the composites upto 350°C beyond which a reverse trend was observed. This was attributed to the catalytic behaviour of CuNPs for early degradation of the composites. The composite films possessed sufficient tensile strength which can replace polymer packaging films like polyethylene. Further, the cellulose/CuNP composite films exhibited good antibacterial activity against E.coli bacteria.

Preparation of cellulose composites with in situ generated copper nanoparticles using leaf extract and their properties.

In the present work, copper nanoparticles (CuNPs) were in situ generated in cellulose matrix using Ocimum sanctum leaf extract as a reducing agent and aq. CuSO4 solution by diffusion process. Some CuNPs were also formed outside the film in the solution which were separated and viewed by Transmission electron microscope and Scanning electron microscope (SEM). The composite films showed good antibacterial activity against Escherichia coli bacteria when the CuNPs were generated using higher concentrated aq. CuSO4 solutions. The cellulose, matrix and the composite films were characterized by Fourier transform infrared spectroscopic, X-ray diffraction, thermogravimetric analysis and SEM techniques. The tensile strength of the composite films was lower than that of the matrix but still higher than the conventional polymers like polyethylene and polypropylene used for packaging applications. These biodegradable composite films can be considered for packaging and medical applications.